The invention relates to a transponder arrangement comprising an interrogation unit which transmits at least one RF interrogation pulse to a responder unit which thereupon sends data stored therein back to the interrogation unit in the form of a modulated RF carrier.
There is a great need for devices or apparatuses which make it possible to identify or detect as regards their presence at a predetermined location objects which are provided with such devices or apparatuses in contactless manner and over a certain distance. It is for example desirable to request contactless and over a certain distance identifications which are uniquely assigned to an object and which are stored in the device or apparatus so that for example it can be determined whether the object is at a predetermined location or not. An example is also the case in which physical parameters such as the temperature or the pressure are to be interrogated directly at or in the object without direct access to the object being possible. A device or apparatus of the type desired can for example be attached to an animal which can then always be identified at an interrogation point without direct contact. There is also a need for a device which when carried by a person permits access checking so that only persons whose responder unit carried by them returns on request certain identification data to the interrogation unit are allowed access to a specific area. In this case the safeguarding of the data transfer is a very essential factor in the production of such devices. A further example of a case in which such a device is needed is the computer-controlled industrial production in which without the intervention of operating personnel components are taken from a store, transported to a production location and there assembled to give a finished product. In this case a device is required which can be attached to the individual components so that the latter can be specifically detected in the spares store and taken from the latter.
In all these examples an transponder arrangement of the type outlined at the beginning is required. For universal usability of such an arrangement the interrogation or inquiry unit must be handy and compact so that it withstands rough treatment in practice. The responder unit must be very small so that it can readily be attached to the objects to be detected.